1. Field of the Invention
This invention relates to a hollow fiber-type artificial lung having an enclosed heat exchanger.
2. Description of the Prior Art
In general, when a patient's blood is conducted extra-corporeally for oxygenation, as in the case of heart surgery, an artificial lung is used in the extra-corporeal circulating circuit. If the patient's blood is circulated through the circuit at ambient or lower temperatures, the blood is cooled during extra-corporeal circulation and therefore must be warmed to the patient's body temperature when exiting from the circuit. For this purpose a heat exchanger is used in the extra-corporeal circulating circuit. The heat exchanger may also be used for cooling the blood when resorting to a low body temperature process.
The prior-art apparatus in which an oxygenator and a heat exchanger are assembled as one unit, is disclosed in U.S. Pat. Nos. 3,807,958 and 4,138,288. In these patents, oxygen is blown into blood for blood oxygenation. This necessitated a defoamer to suppress the resulting foaming of the blood, adding to the size of the overall artificial lung apparatus.
In addition, with the artificial lung disclosed in these patents, the blood guide channel from the blood inlet to the outlet is so complex that the blood flow may undergo excess turbulence with the resulting risk of hemolysis. Moreover, because of the complexity of the guide channel, blood priming may be increased and the defoaming operation during such priming may present major difficulties.
As a solution to this problem, Japanese Patent Publication No. 2982/1980 discloses a stacked membrane type artificial lung having an enclosed heat exchanger. However, the oxygenator section and the heat exchanger section are of the stacked membrane type and are difficult to manufacture. In addition, the membrane type artificial lung may give rise to liquid leakage during use and therefore is not preferred.
At the present time, the hollow fiber type artificial lung is considered to be the device best suited for use as an artificial lung. However, a hollow fiber type artificial lung that has an enclosed heat exchanger has not been known to date.